feat(0004): clarify lowercase in type (#380)

Resource types **must** be lowercase, as the name must be kebab-case. However, it's valuable
to explicitly clarify this.

also fixing some broken links discovered along the way.

Author: toumorokoshi

aep/general/0004/aep.md.j2

@@ -24,10 +24,11 @@ indicated by it's namespacing within the API name.
 
 The type name:
 
-- **must** Only contain ASCII alphanumeric characters.
-- **must** Start with a lowercase letter.
-- **must** Be of the singular form of the resource.
-- **must** Use kebab case.
+- **must** only contain ASCII alphanumeric characters.
+- **must** start with a lowercase letter.
+- **must** be of the singular form of the resource.
+- **must** use kebab case.
+- **must** use all lowercase characters.
 
 ### Examples
 

aep/general/0102/aep.md.j2

@@ -10,8 +10,8 @@ specification in depth.
 An API name is a string that **must** uniquely identify the API. It serves as a
 namespace where elements of an API are defined, including:
 
-- [resource types][/resource-types]
-- [methods][/standard-methods]
+- [resource types](/resource-types)
+- [methods](/standard-methods)
 
 In practice, it is difficult to prevent the re-use of the name across different
 APIs. Therefore the API should use something, such as the domain name of the